Study of the interaction between adsorbed hydrocarbon molecules on graphitized carbon using the chromatographic step-and-pulse method

Abstract

The chromatographic step-and-pulse method has been applied to a study of the adsorption of pure gases and gas mixtures on graphitized carbon black. It is shown how the retention time of a small pulse of a vapour B on a step of preadsorbed vapour A is related to the parameters of an equation of state (two-dimensional van der Waals equation) for the adsorbed gas mixture. The method is used to study the adsorption of isomeric C₆-alkanes, cyclohexane and benzene at 343.2 K. The adsorption isotherms derived for the pure vapours are compared with results obtained by static (gravimetric) measurements. The retention results of B on preadsorbed A are analysed and the bestfit values of the interaction parameter α_AB are derived. These values are found to be smaller than the geometric mean of α_A and α_B for the pure gases.